Conformal Coating Remover: The Ultimate FAQ Guide

 

This guide will teach you how to choose the right conformal coating remover.

Besides, you will learn how to choose the best conformal coating remover, and various techniques you need to know.

So, if you want to be an expert in different types conformal coating, read this guide.

Why Remove Conformal Coating?

Removal of a conformal coating involves the stripping away of a coating to reveal the bare board features.

You find the removal of conformal coating important for a few reasons.

  • You can remove the conformal coating to allow for the execution of repair work on the board to address functionality issues.
  • Removal is also necessary to allow for the replacement of ruined components or their exchange with improved specifications.
  • A coating can also be removed when worn out and no longer capable of offering protection from the elements.
  • Removal of a coating can be attributed to design issues arising from the coating used in the first place.
  • When a coating is established to be of low standard and needs replacement, you can remove it.
  • When a coating is incorrectly applied, it lacks surface uniformity or appropriate thickness and must be redone.

PCB with conformal coating

 Conformal coating

What Determines how to Remove Conformal Coating?

You find there is no standard approach to the removal of a coating.

Different coating materials are employed on printed circuit boards.

For their removal, the following factors are of concern:

  • The type of resin material used for the coating will influence the method of removal.

You find different material have different conformity levels and consequently will need other techniques of disposal.

  • Additionally, the coverage of the coating to be removed will also influence the choice of removal method.

You find a method suitable for a larger area would be unfavorable for a smaller area.

What are the Methods of Removing Conformal Coatings?

There are several techniques used to remove conformal coatings on PCBs.

These techniques involve a range of materials and sometimes equipment. Common methodologies are:

  • Removal by use of solvents.
  • Peeling off the coatings.
  • Burning through the coating.
  • Microblasting
  • Grinding

What Conformal Coating Types can Solvent Remove?

Solvents’ use to remove conformal coatings on PCBs is based on their high reaction to solvent contact.

You find that only solvents that are not damaging to the board can be employed.

Acrylic coatings, epoxy coatings, silicone coatings, and polyurethane coatings are all susceptible to solvent removal.

Among the coatings, you find acrylic coatings to be more responsive to solvent-based removal.

However, parylene coatings are impervious to solvent-based removal.

Consequently, you will need a different removal technique for it.

Why is Grinding not a Common Choice for Removing Conformal Coating?

Also called scraping, grinding is not widespread since its use can result in a damaged circuit board.

You found this method involves the physical grazing of the circuit board to rid it of the coating.

Due to the force involved in scuffing, grinding is typically reserved for tough coatings with strong adhesion.

You will find grinding employed for conformal coatings of the parylene, urethane, and epoxy resin types.

Is Burning Through a Resin suitable as Conformal Coating Removal Technique?

Burning through a resin coating involves heat application using a soldering iron tool.

You find this approach typically employed for minor reworks, such as component replacement.

When using this technique, the board should not have closely packed features.

Where optics are of importance, this method is unfavorable due to the burn marks it leaves behind.

Instead, you can always use other removers.

However, you will find the burn through method applicable with almost all coating types.

Why is the use of Solvent Removal Problematic on Polyurethane Conformal Coatings for PCB?

The use of solvent removal can be applied to acrylic coatings, silicone coatings, and urethane coatings.

While you achieve coating removal more easily with acrylic resins, urethanes are a much tougher nut to crack.

You find a significant cause of the increased difficulty in removing urethane coatings with solvents is their curing process.

These resin coatings undergo heat-induced curing, which makes their adhesion much firmer.

Subsequently, removing them requires tougher solvent compositions.

Removing non conformal coating

Removing non conformal coating

How are Epoxy Conformal Coatings removed from PCBs?

To remove epoxy coatings, you find the combination of two methodologies.

It is common to physically scrub off the epoxy coating first before employing a solvent remover.

You find the firm adhesion of the epoxy resins to the board surface, contributing to this approach.

Also, most epoxy resin coatings are cured by inducing heat forming strong bonds with the board surface.

The physical approach to removing epoxy coatings involves either hand use or micro-ablation.

When using the hand aided approach, coarse material is used to scrub off the layer at the specified areas.

It is significant for small board areas but draining for entire board surfaces.

Micro-ablation employs the use of compressed air to blast abrasive matter onto the surface of the coating.

You find this process faster and can be carried out on a larger body than the hand removal method.

What are the Risks of Physical Removal of Conformal Coating on PCB?

Physical coating removal is justified for tough coatings with strong adhesion to the board.

However, its use can result in a few undesired outcomes.

These include:

  • Applying force on the coating can result in the impairment of component attachments to the board, such as the solder joint.
  • The board’s metal features, such as traces, can also be damaged through the abrasion process.
  • You find the risk of discharge related to electrostatic aspects is profound with these physical approaches.
  • The actions can result in the damaging of other layers, such as the solder mask exposing the underlying features to corrosion.

What is the Plasma Process for Conformal Coating Removal?

Coating removal through the plasma process is a well-defined and accurate procedure used on acrylic and epoxy resins with exceptional results.

You find this process is reserved for premium circuit boards with high-performance levels due to its cost.

Plasma removal can be used to remove the coating on small board areas and the entire board surface.

Furthermore, this process can help you rid the circuit board features and body off of dust particles and other contaminants.

Why is Board Testing necessary after Removing Conformal Coating?

Stripping a circuit board’s coating off entails the use of physical, thermal, or chemical processes.

The processes can all negatively affect the board when carried out and therefore hamper its functionality.

For instance, the solvents used in chemical removal can short a circuit.

Besides, mechanical processes such as scrapping can break wire attachments resulting in broken current flow paths.

Consequently, testing the board after coating removal seeks to ensure the board functionalities are maintained.

What are the Best ways to Remove Silicone Conformal Coating?

Silicone coatings are popularly used due to their ease of application, durability, lightweight, and rework ability.

Furthermore, their protection capability is remarkable.

You also find that silicon coatings are easy to remove, and you can get the job done using solvents.

Some of the solvent removers used for silicone are based on hydrofluorocarbon fluids, which can also be used for solder flux.

You also find flux removers made without volatile organic compounds and serve a dual purpose of cleaning the surface.

What Influences the Effectiveness of Conformal Coating Remover?

Coating removers come in a wide variety with different application methods.

Several factors will influence the ability of a remover to remove a coating on a PCB effectively.

These include:

  • Strength of the remover, especially for chemical-based removers
  • Strength of adhesion of the coating
  • Material constitution of the coating
  • Design of the board, mainly where the coating is to be removed

How is the Strength of a Chemical Solvent for Conformal Coating Remover measured?

You will find two types of chemical solvent removers: those based on water and those that are not.

Consequently, two different measures of strength will be provided for distinct categories.

Water-based solvents are evaluated by their pH value, whereas the Kauri-Butanol (Kb) value is appropriate for non-aqueous solvents.

The pH value is a measure that is provided with values from 0 to 14.

You find pH values to describe the strength of a solvent as an acid or a base.

Here, water is used as the standard base of comparison with seven regarded as neutral.

Values lower than seven are considered acidic while those higher are deemed necessary.

The Kb value is a measure of strength for solvent removers that are non-aqueous.

To determine solvent remover’s Kb value, butanol is submerged in the solvent under defined environmental conditions for a specified period.

Butanol is thereafter removed, and the amount dissolved is determined.

You find that the strength of the solvent is measured by how much butanol was dissolved.

Consequently, a large amount of butanol material dissolved signifies a robust chemical solvent remover and a higher Kb value.

The Kb value can range anywhere from as low as 10, representing a weak remover to over 200.

What are the Chemical Solvent used for Conformal Coating Removal?

Chemical solvents are derived from combinations of chemical substances under different conditions to achieve other property specifications.

When using chemical solvents, they can be used to submerge features with coatings removed or applied by cloth brushes.

Typical solvents used include:

Removing conformal coating on PCB

Removing conformal coating on PCB

  • Ethylene glycol: Using this solvent is incredibly productive when combined with ether or methanol alkaline. They are markedly helpful when removing urethanes.
  • Methylene chloride: You find this chemical solvent suitable on silicone coatings inducing very little corrosion on interaction.
  • Butyrolactone: This chemical solvent is highly efficient on acrylic-based conformal coatings.
  • Tetrahydrofuran: Other chemical solvents are particularly appropriate for only a single coating material. However, this chemical solvent can be used on all coating materials.

How are Acrylic Conformal Coating Removed?

Acrylic coatings pose a challenge in their removal due to their strong adhesion to the board surface.

You find removing such layers will require powerful flux removers whose Kb value is immense.

However, these removers can dry up rapidly, necessitating the soaking of the solvent’s coating features.

Furthermore, you can shield the areas to which the solvent remover is applied to reduce their evaporation rate.

In the case of total immersion of the coated feature, you can cover the basin’s top.

Where can you use an Uncured Remover?

An uncured remover is useful in the conformal coating removal of robust coatings such as polyurethanes and uncured epoxies.

Due to the difficulty in removing these coatings, they are soaked in uncured removers with a high Kb value.

You find these removers need to have slow drying; otherwise, they should be covered to minimize evaporation.

What are the Steps Involved in using Chemical Solvent Conformal Removers?

You find the following steps typical in the removal of coatings using chemical solvent removers:

  • The board area where the coating is to be removed is bordered by using a tape with a high-temperature quality.
  • You will then apply the solvent remover to this area through a cloth brush. Repeat the procedure to reduce the effect of quick-drying until the coating is soaked.
  • Upon soaking of the wetted area, use a bristled brush to remove the coating. You can use flat pieces of equipment such as blades to wedge off the layer for polyurethanes and thick layers.
  • When you have removed the coating, you can clean and dry the surface.

How is the Thermal Method Effectively used for Conformal Coating Removal?

To effectively use thermal techniques to remove a PCB coating, the temperature values have to be low.

The essence is to generate just enough heat to smolder and melt the coat without destroying the underlying surface.

You find employing a soldering iron device will not achieve a low-temperature burn-through and, as such, is not advisable.

When using the thermal technique, remember to protect yourself from the resulting fumes.

Burning of polymer materials produces oxides of carbon, which can cause health complications.

You can wear a gas mask and work in a well-ventilated area as a precautionary measure.

The steps involved in an effective thermal-based coating removal technique include:

  • To initiate the burn process, use a thermal tip with the required temperature value.
  • Lightly apply the device on the coating to smolder it. You find the reaction to the heat depends on the material composition of the coating. Whereas epoxy resins fragment urethanes melt into a soft state.
  • The amount of time you apply the thermal stick to the coating depends on the material’s thickness and toughness. As the layer melts away, reduce the tip’s temperature as you get closer to the board surface.
  • To break the adhesion forces between the coating and the board, you can also use a blast of hot air. You minimize the risk of burning the board surface this way.

What Tools and Equipment are used for the Grinding in Conformal Coating Removal Method?

Grinding applies abrasive force to rid the circuit board surface of its coating.

Since this method requires the generation of frictional forces, electrostatic discharges are bound to occur.

To scrape off the coating, several different equipment and tools can be used to aid the process.

  • You can use a blade to scrape thick coatings.
  • A rubber-based abrasive rotated by a motor can help you scrub off thin coatings that are rigid.
  • A rotating brush tool is efficient to help you scuff off lax coatings.
  • You can use a paper with a granular surface to scrub of thin coatings.

What are the main Steps in Micro Blaster Conformal Coating Removal?

To remove a coating using a micro blaster, fine particles of an abrasive substance are used.

You pack this powder in the blaster machine where they are targeted to the layer.

You need to ensure the blaster is capable of handling static electric discharge to prevent component failure.

The typical procedures carried out are as follows:

  • You need to clean the surface where the coating is to be removed. The micro blaster process is typically applied for small intricate areas.
  • After that, you pick a suitable nozzle to suit the application area and fix it to the blaster containing the abrasive particles.

Compressed air is used to propel the particles, and therefore you need to select the appropriate pressure.

The resulting force applied will depend on the thickness and toughness of the coating.

  • You need to mask the other board areas whose coating is not to be removed for selective coating removal.

You can use adhesive tapes stencils or liquid-based masks.

Where the area of coating removal is small, you can use a cover bag to protect the whole board.

In turn, a small opening is made to reveal the part of coating removal.

  • To prevent the damage of electronic components, you have to connect the PCB to a ground wire.

The static charges generated by the process are safely conducted this way.

  • Subsequently, you can put the circuit board into the micro blaster where you will guide the process by directing the nozzle.
  • Upon completing the process, you can use a blower to remove the dust and coating fragments.

This is sufficient since micro blasting is a dry process. For a cleaner finish, you can use solvent cleaners.

What are the Advantages of Using Micro Blasting Conformal Coating Removal?

You find many benefits in employing micro blasting removers.

Some of these benefits are:

Conformal coating

Conformal coating

  • Micro blasting offers you an elaborate and dependable coating removal technique for small and sensitive areas.
  • To carry out micro blasting, you do not require advanced skill levels. Furthermore, you can control the process allowing you to achieve the accuracy you desire.
  • Other methods of coating removal, such as chemical methods, can negatively impact the environment. Micro blasting is a safe method that is not harmful to the environment.
  • Micro blasting can be employed on several conformal coatings and in applications where sensitivity to static discharges is concerned.

Are Lasers used in Conformal Coating Removal?

Yes.

Laser ablation is a coating removal process that uses laser radiation to aid in removing a conformal coating.

The laser light shaft can mark out areas for coating removal and cut and bore through the layer.

Furthermore, you find the accuracy levels involved in the laser ablation process are very high.

Therefore, you find laser ablation convenient on highly populated boards where efficient masking is improbable.

Additionally, it can be used on any thick and hard coating, including parylene.

However, its use is costly and uneconomical for small repairs.

At Venture Electronics, we help you choose the right conformal coating remover.

Contact us today for all your PCB fabrication needs.

We guarantee high performance and affordable PCB designs.

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